In screw machines such as refrigerant compressors, the refrigerant being compressed tends to move the screw rotors towards the suction side and away from the discharge side. Because separation of the rotors from the discharge side represents a leak passage, the discharge side bearings and related structure tend to severely limit movement of the rotors away from the discharge. Commonly assigned U.S. Pat. No. 5,975,867 discloses structure associated with the discharge side bearings for limiting movement of the screw rotors. The suction side bearings are much less loaded due to the movement restraint applied to the rotors by the discharge side bearings and their related structure. The suction or inlet side bearings are free to move in the direction of rotation of the rotors they support. They hold the position of the rotors only in their radial direction.
The suction side bearings are located in a diametrically extending bridge or webbing located between the motor and screw rotors so as to provide support for the inlet or suction side bearings, and thereby the screw rotors, while permitting fluid communication between the motor chamber and the suction of the compressor via flow around the bridge or webbing. Additionally, the bridge typically provides a portion of the inlet bearing lubrication paths in combination with external lines and/or xe2x80x9cgun drillingxe2x80x9d in the compressor housing structure.
There is an affinity between refrigerants and lubricants such that the refrigerant in a refrigeration system normally has some oil therein. According to the teachings of the present invention, the inlet bearings are supported in an open structure such that they are exposed to and thereby lubricated and cooled by the oil containing suction and motor cooling flow as it passes from the motor/suction chamber to the inlets of the coacting pair(s) of rotors.
It is an object of this invention to eliminate separate lubrication structure for the inlet bearings.
It is another object of this invention to simplify manufacture and reduce manufacturing costs. These objects, and others as will become apparent hereinafter, are accomplished by the present invention.
Basically, the inlet bearings of a screw machine, such as a refrigerant compressor, are both lubricated and cooled by a portion of the motor cooling and suction flow which has lubricant entrained therein and which is drawn through the inlet bearings into the coacting pair(s) of screw rotors.